1. Field of the Invention
The present invention relates to a mobile communications system and an operation control method therefor, and a node and a wireless control apparatus for use in the system and method, and more specifically to a mobile communications system using a VoIP (voice over Internet protocol) technology and an operation control method therefor, and a node and a wireless control apparatus for use in the system and method.
2. Description of the Related Art
The core network in the current mobile communications system separately includes a CS (Circuit Switched) network which is a network for audio communications and has a circuit switched function, and a PS (Packet Switched) network which is a network for packet communications and has a packet switched function. The core network is standardized by the 3GPP (3rd generation partnership project), and indicated by a function block as shown in FIG. 8.
In FIG. 8, a core network (CN) 1 includes a CS network 2 and a PS network 3. The CS network 2 includes an MSC (mobile-services switching center) 21 having a circuit switched function and a GMSC (gateway MSC) 22 having a gateway function. The PS network 3 includes an SGSN (serving GPRS (global packet radio service) support node) 31, and a GGSN (gateway GPRS support node) 32 having a gateway function. The core network 1 is provided with an HLR (home location resister) 4 for management of the position of a mobile communications unit (user equipment (UE)) 10, and the HLR 4 can be accessed by the MSC, GMSC, SGSN, and GGSN.
An RAN (radio access network) 9 is provided between the core network 1 and the user equipment 10, and the RAN 9 includes an RNC (radio network controller) 91 which is a wireless control apparatus. A wireless bearer 100 is provided between a Node B (not shown in the attached drawings) which is a wireless base station in the RAN 9 and the UE 10 so that audio and packet communications can be performed.
The CS network 2 of the core network 1 is connected to a PSTN (public switched telephone network) 5. The PS network 3 is connected to the Internet 7 through an IP (Internet protocol) network 6 (or directly). The PS network 3 is connected to the PSTN 5 through the IP network 6 and a PSTN connection network 8. The PSTN connection network 8 includes equipments for realizing a fixed telephone network VoIP which is currently put to practical use.
FIG. 9 is a block diagram showing the SGSN 31 and the GGSN 32 forming the PS network 3 in the core network 1 and the peripheral equipments shown in FIG. 8. The SGSN 31 includes a CPU (also referred to as a CP which is short for a call processor) 311 as a control device for controlling signaling on a PS call, and a PS-UP (PS side user plane device) 312 for processing control on user data relating to the PS call. The CPU 311 controls signaling on the PS call, communicates a signaling with the RNC 91 and the GGSN 32 to control the PS-UP 312. The PS-UP 312 communicates user data with the RNC 91 and the GGSN 32 under the control of the CPU 311.
The PSTN connection network 8 also realizes the fixed telephone network VoIP as described above. To attain this, it includes a CA (call agent) 81, an MGC (media gateway controller) 83, an MGW (media gateway) 82, etc. The CA 81 controls a call, the MGW 82 transcodes between IP side audio data and PSTN side audio data, and the MGC 83 controls the MGW 82 based on the control by the CA 81.
In the mobile communications system having the above-mentioned system architecture, the technology of realizing a VoIP using a PS network which is a network for packet communications has been investigated. There also is the technology of connecting a PLMN (public land mobile network) IP core between the RNC and the MGW in the mobile communications system to realize a VoIP so that the real-time traffic from a mobile unit can be routed using the PLMNIP core and a VoIP of the mobile unit can be realized without passing through a GGSN which is a gateway for a GPRS (for example, Japanese Patent Application Laid-Open No. 2002-44740).
The VoIP technology currently put to practical use using the PSTN connection network 8 shown in FIGS. 8 and 9 is not intended for a mobile unit, but for a fixed telephone network VoIP using a fixed telephone, and the application of the VoIP technology is being investigated in the mobile communications system using the mobile communications unit as described above. In this case, the VoIP is realized using the PS network shown in FIG. 8. However, since the RAN 9 and the PS network 3 which are mobile communications networks are simple access networks connected to the IP network 6, they cannot determine whether a call from the user equipment 10 is for data communications or VoIP communications.
Additionally, in this case, a packet communications circuit is used as a wireless circuit with which the wireless bearer 100 is set between the user equipment 10 and the RAN 9. However, using a packet communications circuit as a wireless circuit causes the problems that the use efficiency of the wireless circuit is lowered and that it is difficult to control the band of the wireless circuit.
The reasons for the above-mentioned problems are described below. That is, when the wireless circuit is connected from the user equipment 10 and terminated by the RNC 91 through the Node B in the RAN 9 (base station not shown in the attached drawings), a band of a maximum of 12.2 kbps and a band for headers per user are reserved in the audio communications using the CS network 2. If the traffic of mobile units concentrates on one area, a method of increasing the number of available mobile units is used with the band per user limited. When the PS network 3 is used, the available band possibly varies constantly because some user uses various bands. Furthermore, if there are users who transfer a large volume of data, there can be the possibility that available bands are constantly very narrow. Although in the current technology, when the PS network is used, there are some services such as transmitting data without delay, without error, with best effort, etc. depending on the class of each service called QoS (quality of service), the fine band control of a wireless circuit which can be performed using the CS network cannot be realized.
The technology disclosed by Japanese Patent Application Laid-open No. 2002-44740 is intended for realizing a VoIP of a mobile communications unit by providing a PLMNIP core between an RNC and an MGW, but does not disclose in detail a practical example of realizing the VoIP, etc., and does not clearly describe whether or not it uses a packet communications circuit as a wireless circuit, thereby leaving the above-mentioned problems unsolved.